Naval hero (6)
I believe the answer is:
nelson
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">naval hero</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for nelson that I've seen before include "'Horatio ..., English admiral (6)'" , "Maritime chief" , "Trafalgar victor" , "Hero of Trafalgar Square" , "Horatio ..., British admiral" .)